O2

My contract ended in May. I never got in touch with 02 as I had thought it would automatically end. However now I have received an email saying a bill is unpaid and they'll be disconnecting the device also that there is a termination charge of £30.14...

I received my monthly bill and it's saying the balance is £16.50 which is strange because my usual bills are around £40 mark. When I went into the breakdown it says 'balance brought forward -£30.80'. I'm not sure what that means? Do I only owe £16 or...